Conventional rolling bearing units of the type shown in FIG. 7 are used for rotatably supporting a vehicle wheel and detecting its rotational speed.
In FIG. 7, an inner ring assembly comprises a hub 1, an inner ring 4 which is fittingly engaged on an axially inner end portion (right end portion in FIG. 7) of the hub 1 and a nut 5 which is provided on the axially inner side of the hub 1.
The hub 1 has a flange 2 radially extending from an outer peripheral surface thereof for supporting a wheel and a disc rotor of a brake unit (not shown). A first inner raceway 3a is formed directly on an axially central portion of the outer peripheral surface of the hub 1, and a second inner raceway 3b is formed on an outer peripheral surface of the inner ring 4. A shoulder portion 6 is formed on an outer peripheral surface of the hub 1 between the first and second raceways 3a and 3b, so that the axially outer face of the inner ring 4 abutts the axially inner face of the shoulder portion 6.
The nut 5 is threaded onto a male-threaded portion formed on the outer peripheral surface of the axially inner end portion of the hub 1, and the inner ring 4 is fixedly clamped between the nut 5 and the shoulder portion 6.
A cylindrical portion 7 with a cylindrical outer peripheral surface is formed on the axially inner end of the hub 1 so as to protrude axially inward through the nut 5 (toward the right in FIG. 7).
A disk-shaped or annular pulse rotor 8 is made of a magnetic material such as a steel and press-fitted onto the protruding cylindrical portion 7.
A ribbed portion 9 having alternate grooves and ridges in a circumferential direction is formed on the axially inner face (right side face in FIG. 7) of the pulse rotor 8.
An outer ring assembly comprises a cylindrical outer ring 10 which is provided around the hub 1 with a space 15 therebetween. The outer ring 10 is provided with a flange 11 radially extending from an outer peripheral surface thereof and connected to a suspension unit knuckle (not shown) by means of the flange 11. First and second outer raceways 12a and 12b are formed on respective portions of the inner peripheral surface of the outer ring 10 to mate with the first and second inner raceways 3a and 3b, respectively. A plurality of rolling bodies (e.g., ball bearings) 13 are provided in the space 15 between the inner raceways 3a and 3b and the outer raceways 12a and 12b, so that the hub 1 is free to rotate inside the outer ring 10.
A seal 14 is supported in the opening section of the axially outer end (left end in FIG. 7) of the ring 10. The seal 14 has an inner rim with an elastic member which comes into slidable contact with a circumferential portion of the outer peripheral surface of the hub 1, so that the outer end opening of the space 15 to accommodate the plurality of rolling bodies 13 is sealingly covered. The axially inner end portion (right end in FIG. 7) of the outer ring 10 is provided with a metal cover 16 formed through deep drawing and engagingly fitted into the opening of the axially inner end portion of the outer ring 10. A sensor 17 for sensing rotational speed is fixed into the metal cover 16 so as to face the ribbed portion 9 on the pulse rotor 8.
With the rolling bearing unit for sensing rotational speed constructed as above, the hub 1 is able to rotate inside the outer ring 10 due to rotation of the plurality of rolling bodies 13 provided respectively between the inner raceways 3a and 3b and the outer raceways 12a and 12b, and the rotational speed of the hub 1 can be sensed by the sensor 17.
The output from the sensor 17 changes in accordance with the change in distance between a first or axially outer end face of the sensor 17 (left end in FIG. 7) and the surface of the ribbed portion 9 on a second or axially inner end face of the pulse rotor 8. The frequency of the change in output is proportional to the rotational speed of the hub 1 to which the pulse rotor 8 is fixed. Hence if the signal from the sensor 17 is input to a controller (not shown in the figure), the rotational speed of a wheel mounted on the hub 1 can be determined and used to control an antiskid or antilock braking system (ABS) or a traction control system (TCS).
With the rolling bearing unit for sensing rotational speed constructed as above, the signal detected by the sensor 17 and representing the rotational speed of the hub 1 is sent to a controller through a plug connector means. For example, as disclosed in First Publication of European Patent Application No. 0,401,464A2, a synthetic resin connector 18 is provided outside the cover 16 and directed radially as illustrated by dotted lines in the drawing for connection to a plug on the end of a lead to the controller. The synthetic resin connector 18 is formed integral with the synthetic resin body 19 in which the sensor 17 is embedded.
With the conventional rolling bearing unit constructed as above, however, the synthetic resin connector 18 is left exposed outside the metal cover 16. As a result, it is easily bumped against components, such as the knuckle, when the rolling bearing unit is being fitted onto the suspension unit. Hence, it may be easily deformed or damaged. If this occurs, it may be difficult or impossible to connect the mating plug with the synthetic resin connector 18.
There is also the possibility that the synthetic resin connector 18 may be damaged when connected with the mating plug during driving. This may occur when flying stones strike the synthetic resin connector 18 with high impact, thereby resulting in broken wires, insulation damage, and faulty connection.